Magnetic disk device

ABSTRACT

According to one embodiment, a magnetic disk includes a disk, first and second heads which write data to the disk and read data from the disk, a first actuator includes the first head, a second actuator includes the second head, first and second controllers which control the first head, the second head, the first actuator and the second actuator, an auxiliary power supply which supplies power when power from a power supply is shut off, and a power supply detection unit which makes power supplied from the auxiliary power supply to the first controller higher than the power supplied from the auxiliary power supply to the second controller when shutoff of power from the power supply is detected.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2019-051325, filed Mar. 19, 2019, theentire contents of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to a magnetic disk device.

BACKGROUND

Recently, the number of magnetic disks has increased in connection withthe increase in the recording capacity of magnetic disk devices. To dealwith the increase in the number of magnetic disks, a multiactuatormagnetic disk device, which comprises a plurality of, for example, twoactuators, is suggested. Multiactuator magnetic disk devices eachcomprise a plurality of controllers to independently control a pluralityof actuators. Therefore, multiactuator magnetic disk devices may consumemore electricity than normal magnetic disk devices which each comprise asingle actuator. In multiactuator magnetic disk devices, when power froma power supply is shut off or reduced, a power loss protection (PLP)process may be interrupted by a steep drop in voltage.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the structure of a magnetic diskdevice according to a first embodiment.

FIG. 2 is a block diagram showing an example of a PLP circuit accordingto the first embodiment.

FIG. 3 is a timing chart showing an example of the PLP process of thePLP circuit shown in FIG. 2.

FIG. 4 is a block diagram showing an example of a PLP circuit accordingto a second embodiment.

FIG. 5 is a timing chart showing an example of the PLP process of thePLP circuit shown in FIG. 4.

FIG. 6 is a block diagram showing an example of a PLP circuit accordingto a third embodiment.

FIG. 7 is a timing chart showing an example of the PLP process of thePLP circuit shown in FIG. 6.

FIG. 8 is a block diagram showing an example of a PLP circuit accordingto a fourth embodiment.

FIG. 9 is a timing chart showing an example of the PLP process of thePLP circuit shown in FIG. 8.

FIG. 10 is a block diagram showing the structure of a magnetic diskdevice according to a fifth embodiment.

FIG. 11 is a block diagram showing an example of a PLP circuit accordingto the fifth embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, a magnetic disk devicecomprises: a disk; first and second heads which write data to the diskand read data from the disk; a first actuator comprising the first head;a second actuator comprising the second head; first and secondcontrollers which control the first head, the second head, the firstactuator and the second actuator; an auxiliary power supply whichsupplies power when power from a power supply is shut off; and a powersupply detection unit which makes power supplied from the auxiliarypower supply to the first controller higher than the power supplied fromthe auxiliary power supply to the second controller when shutoff ofpower from the power supply is detected.

Embodiments will be described hereinafter with reference to theaccompanying drawings. The drawings are merely examples and do not limitthe scope of the invention.

First Embodiment

FIG. 1 is a block diagram showing the structure of a magnetic diskdevice 1 according to a first embodiment.

The magnetic disk device 1 comprises a head-disk assembly (HDA) asdescribed later, a driver integrated circuit (IC) 20, a head amplifierintegrated circuit (a head amplifier IC or a preamplifier) 30, avolatile memory 70, a buffer memory (buffer) 80, a nonvolatile memory 90and a system controller 130 which is a single-chip integrated circuit.The magnetic disk device 1 is connected to a host system (simply, ahost) 100. The magnetic disk device 1 is a multiactuator magnetic diskdevice comprising a plurality of, for example, two actuators 16 asdescribed later. The magnetic disk device 1 may comprise more than twoactuators 16. The magnetic disk device 1 may be a normal disk devicecomprising a single actuator 16.

The HDA comprises a magnetic disk (disk) 10, a spindle motor (SPM) 12,an arm 13 comprising a head 15, and a voice coil motor (VCM) 14. Thedisk 10 is attached to the spindle motor 12, and rotates when thespindle motor 12 is driven. The arm 13 comprises, for example, arms 13Aand 13B. The VCM 14 comprises, for example, VCMs 14A and 14B. The head15 comprises, for example, heads 15A and 15B. An actuator 16A comprisesthe arm 13A and the VCM 14A. An actuator 16B comprises the arm 13B andthe VCM 14B. The actuator 16A drives the VCM 14A to move the head 15Amounted on the arm 13A to the target position on the disk 10. Theactuator 16B drives the VCM 14B to move the head 15B mounted on the arm13B to the target position on the disk 10. The actuators 16A and 16B areattached to the common pivot shaft, and are configured to independentlyrotate around the pivot shaft from each other. Two or more disks 10 maybe provided. Each of the heads 15A and 15B may comprise two or moreheads. Three or more arms 13, VCMs 14 and heads 15 may be provided.

A user data area 10 a available to the user and a system area 10 b towhich information necessary for system management is written areallocated to an area of the disk 10 to which data can be written. Adirection perpendicular to the radial direction of the disk 10 isreferred to as a circumferential direction.

The head 15A comprises a slider as the main body, and further comprisesa write head 15WA and a read head 15RA mounted on the slider. The head15B comprises a slider as the main body, and further comprises a writehead 15WB and a read head 15RB mounted on the slider. The write heads15WA and 15WB write data to the disk 10. The read heads 15RA and 15RBread the data stored in the data tracks of the disk 10.

The driver IC 20 controls the drive of the SPM 12 and the VCM 14 inaccordance with the control of the system controller 130 (in detail, anMPU 60 as described later). The driver IC 20 comprises a PLP powersupply (auxiliary power supply) 21 as a backup power supply. When powerfrom the power supply of the magnetic disk device 1 (simply, a powersupply) is shut off, or when power from the power supply is reduced, thePLP power supply 21 supplies power necessary to maintain the minimumoperation of the magnetic disk device 1.

The head amplifier IC (preamplifier) 30 comprises a read amplifier and awrite driver. The read amplifier amplifies the read signal read from thedisk 10 and outputs the read signal to the system controller 130 (indetail, a read/write [R/W] channel 40 as described later). The writedriver outputs write current to the head 15 in accordance with thesignal output from the R/W channel 40.

The volatile memory 70 is a semiconductor memory in which data is lostwhen power supply is shut off. The volatile memory 70 stores datanecessary for the processes of the units of the magnetic disk device 1,etc. The volatile memory 70 is, for example, a dynamic random accessmemory (DRAM) or a synchronous dynamic random access memory (SDRAM).

The buffer memory 80 is a semiconductor memory in which, for example,the data transferred between the magnetic disk device 1 and the host 100is temporarily stored. The buffer memory 80 may be integrally structuredwith the volatile memory 70. The buffer memory 80 is, for example, aDRAM, a static random access memory (SRAM), an SDRAM, a ferroelectricrandom access memory (FeRAM) or a magnetoresistive random access memory(MRAM).

The nonvolatile memory 90 is a semiconductor memory in which the storeddata is maintained even when power supply is shut off. The nonvolatilememory 90 is, for example, a NOR or NAND flash read only memory (flashROM or FROM).

The system controller (controller) 130 is realized by, for example,using a large-scale integrated circuit (LSI) called a System-on-a-Chip(SoC), in which a plurality of elements are integrated in a single chip.The system controller 130 is electrically connected to the driver IC 20,the head amplifier IC 30, the volatile memory 70, the buffer memory 80,the nonvolatile memory 90 and the host system 100. The system controller130 comprises, for example, system controllers 130A and 130B. In theexample shown in FIG. 1, the system controller 130A is electricallyconnected to the volatile memory 70, the buffer memory (buffer) 80 andthe nonvolatile memory 90.

FIG. 2 is a block diagram showing an example of a PLP circuit CRTaccording to the present embodiment.

The PLP circuit CRT is a circuit for performing a PLP process. The PLPcircuit CRT comprises, for example, the PLP power supply 21, the buffermemory 80, the nonvolatile memory 90, the system controllers 130A and130B, a power supply 201, a regulator 202, a servo component (SVC) 203and a regulator (slave regulator) 204. Hereinafter, the regulator 202may be referred to as a power supply unit 202. The SVC 203 may bereferred to as a power supply detection unit 203. The regulator 204 maybe referred to as a power supply unit 204. The PLP circuit CRT mayfurther comprise the volatile memory 70.

The power supply 201 is, for example, a 5 V eFuse. The power supply 201is electrically connected to the regulator 202, the SVC 203 and theregulator 204. The power supply 201 supplies electricity (power) to theregulator 202, the SVC 203 and the regulator 204. For example, the powersupply 201 supplies a power of 5 V to each of the regulator 202, the SVC203 and the regulator 204.

The regulator 202 comprises a DCDC enable pin EN1. The regulator 202 isequivalent to, for example, a master regulator with respect to theregulator 204. The regulator 202 is electrically connected to the systemcontroller 130A. The regulator 202 outputs a particular voltage orcurrent, for example, a fixed voltage, to the system controller 130A.For example, the regulator 202 outputs a voltage of 1 V to the systemcontroller 130A.

The SVC 203 is electrically connected to the PLP power supply 21, thepower supply 201, the DCDC enable pin EN1 of the regulator 202, thesystem controller 130A, the system controller 130B and the enable pinEN2 of the regulator 204. For example, the SVC 203 outputs 1.8 V and 1.5V to each of the system controllers 130A and 130B. When the shutoff ofor reduction in power from the power supply 201 is detected, the SVC 203reduces at least the power supplied to the system controller 130B. Inother words, when the shutoff of or reduction in power from the powersupply 201 is detected, the SVC 203 makes the power supply amount to thesystem controller 130A higher than the power supply amount to the systemcontroller 130B. The operation of “making the power supply amount to thesystem controller 130A higher than the power supply amount to the systemcontroller 130B” includes making the power supply amount to the systemcontroller 130B to be zero without changing the power supply amount tothe system controller 130B. When the shutoff of or reduction in powerfrom the power supply 201 is detected, for example, the SVC 203 outputsa fault signal to the regulator 204 and the system controllers 130A and130B. When the shutoff of or reduction in power from the power supply201 is detected, the SVC 203 outputs a signal to activate the PLP powersupply 21 (hereinafter referred to as activation signal) to the PLPpower supply 21.

The regulator 204 comprises the enable pin EN2. The regulator 204 isequivalent to a slave regulator with respect to the regulator 202. Theregulator 204 is electrically connected to the system controller 130B.The regulator 204 outputs a particular voltage or current, for example,a fixed voltage, to the system controller 130B. For example, theregulator 204 outputs a voltage of 1 V to the system controller 130B.When the regulator 204 receives a fault signal in the enable pin EN2from the SVC 203, the operation of the regulator 204 is stopped (inother words, the regulator 204 is disabled).

The PLP power supply 21 is structured by counter electromotive forcesupplied from the spindle motor 12 shown in FIG. 1, the retention chargeof a capacitor (not shown), etc. The PLP power supply 21 is electricallyconnected to the regulator 202, the SVC 203 and the regulator 204. Whenan activation signal is received from the SVC 203, the PLP power supply21 is activated and supplies power to at least the regulator 202. Forexample, when an activation signal is received from the SVC 203, the PLPpower supply 21 is activated to makes the power supply amount to theregulator 202 higher than the regulator 204. The operation of “makingthe power supply amount to the regulator 202 higher than the regulator204” includes making the power supply amount to the regulator 204 to bezero without changing the power supply amount to the regulator 204.

The buffer memory 80 is connected to the system controller 130A. Thebuffer memory 80 temporarily stores cache data, for example, of thewrite data to be written to the disk 10 by an instruction from the host100, data which is not written to the disk 10. The buffer memory 80 maybe included in the volatile memory 70. In place of the buffer memory 80,the volatile memory 70 may be connected to the system controller 130A.

The nonvolatile memory 90 is connected to the system controller 130A.When the shutoff of or reduction in power from the power supply 201 isdetected, the nonvolatile memory 90 stores the cache data stored in thebuffer memory 80.

The system controller 130A is equivalent to, for example, a master SoCwith respect to the system controller 130B. The system controller 130Acomprises an R/W channel 40A, a central processing unit (CPU) 60A and aserial interface SRA. The system controller 130A is electricallyconnected to the buffer memory 80 and the nonvolatile memory 90. Thesystem controller 130A is connected to the serial interface SRB of thesystem controller 130B as described later via the serial interface SRA.When the shutoff of or reduction in power from the power supply 201 isdetected, for example, when a fault signal is received from the SVC 203,the system controller 130A performs a backup process for saving thecache data stored in the buffer memory to the nonvolatile memory 90.

The R/W channel 40A performs a signal process of read data transferredfrom the disk 10 to the host 100 and write data transferred from thehost 100 in response to an instruction from the MPU 60A as describedlater. The R/W channel 40A comprises a circuit or function forevaluating the signal quality of read data.

The CPU 60A is a main controller which controls the units of themagnetic disk device 1 in response to an instruction from the host 100,etc. For example, the CPU 60A performs servo control by controlling theactuator 16A via the driver IC 20 to determine the position of the head15A. For example, the CPU 60A may perform servo control by controllingthe actuator 16B via the driver IC 20 to determine the position of thehead 15B. The CPU 60A controls data write to the disk 10 and selects thestorage destination of write data. The CPU 60A controls data read fromthe disk 10 and controls the process of read data. The CPU 60A isconnected to the units of the magnetic disk device 1. The CPU 60A iselectrically connected to, for example, the driver IC 20 and the R/Wchannel 40A.

The serial interface SRA is a high-speed serial interface, which enableshigh-speed serial communication.

The system controller 130B is equivalent to, for example, a slave SoCwith respect to the system controller 130A. The system controller 130Bcomprises an R/W channel 40B, a CPU 60B and the serial interface SRB.When the operation of the regulator 204 is stopped (in other words, whenthe regulator 204 is disabled), the operation of the system controller130B is stopped (off) as the power supplied from the regulator 204 isshut off.

The R/W channel 40B performs a signal process of read data transferredfrom the disk 10 to the host 100 and write data transferred from thehost 100 in response to an instruction from the CPU 60B as describedlater. The R/W channel 40B comprises a circuit or function forevaluating the signal quality of read data.

The CPU 60B is a main controller which controls the units of themagnetic disk device 1 in response to an instruction from the host 100,etc. For example, the CPU 60B performs servo control by controlling theactuator 16B via the driver IC 20 to determine the position of the head15B. For example, the CPU 60B may perform servo control by controllingthe actuator 16A via the driver IC 20 to determine the position of thehead 15A. The CPU 60B controls data write to the disk 10 and selects thestorage destination of write data. The CPU 60B controls data read fromthe disk 10 and controls the process of read data. The CPU 60B isconnected to the units of the magnetic disk device 1. The CPU 60B iselectrically connected to, for example, the driver IC 20 and the R/Wchannel 40B.

The serial interface SRB comprises a structure similar to that of theserial interface SRA.

FIG. 3 is a timing chart showing an example of the PLP process of thePLP circuit CRT shown in FIG. 2. In FIG. 3, the horizontal axisrepresents time. In FIG. 3, the arrow shows the passage of time. Thehorizontal axis of FIG. 3 indicates that the SVC detects the shutoff ofor reduction in a power of 5 V (electricity) supplied from the powersupply 201, in other words, timing T1 at which a fault signal outputfrom the SVC 203 is detected, and timing T2 at which the PLP powersupply 21 is activated. FIG. 3 shows the power from the power supply 201(5 V), the voltage when the SVC 203 detects the shutoff of or reductionin power from the power supply 201 or the voltage when a fault signaloutput from the SVC is detected (SVC Fault Detection Voltage), thevoltage at which the low-voltage abnormal operation prevention function(Under Voltage Lock Out [UVLO]) of the regulator 202 operates (MasterRegulator UVLO), ground voltage (GND), a fault signal (Fault), theenable of the regulator 204 (Slave Regulator Enable), the PLP powersupply 21 (PLP Power Supply) and the reset of the system controller 130A(Master SoC Reset).

In the examples shown in FIG. 2 and FIG. 3, when the shutoff of orreduction in power from the power supply 201 is detected at timing T1,the SVC 203 outputs a fault signal to the system controller 130A, thesystem controller 130B and the enable pin EN2 of the regulator 204. Whena fault signal is received from the SVC 203 at timing T1, the operationof the regulator 204 is stopped. As power is not supplied from theregulator 204, the operation of the system controller 130B is stopped.When the shutoff of or reduction in power from the power supply 201 isdetected at timing T1, the SVC 203 outputs an activation signal to thePLP power supply. When an activation signal is received from the SVC203, the PLP power supply 21 is activated at timing T2. The PLP powersupply 21 supplies power to the regulator 202 to maintain the operationof the system controller 130A. It is possible to prevent theinterruption of a PLP process by activating the PLP power supply 21 attiming T2 before the voltage of the regulator 202 reaches the masterregulator UVLO. In this way, before the UVLO of the regulator 202operates, the PLP power supply 21 is activated, and further, the systemcontroller 130B is stopped. Thus, the system controller 130A isconfigured to perform a backup process for storing, in the nonvolatilememory 90, the cache data temporarily stored in the buffer memory 80without interrupting a PLP process.

In the present embodiment, the magnetic disk device 1 comprises the arm13A comprising the head 15A, the arm 13B comprising the head 15B, theVCM 14A, the VCM 14B, the power supply 201, the regulator 202, the SVC203, the regulator 204, the PLP power supply 21, the buffer memory 80,the nonvolatile memory 90, the system controller 130A and the systemcontroller 130B. The power supply 201 is electrically connected to theregulator 202, the regulator 204 and the SVC 203. The regulator 202 iselectrically connected to the system controller 130A. The regulator 204is electrically connected to the system controller 130B. The SVC 203 iselectrically connected to the enable pin EN1 of the regulator 202. TheSVC 203 is electrically connected to the enable pin EN2 of the regulator204. The SVC 203 is electrically connected to the PLP power supply 21.The SVC 203 is electrically connected to the system controllers 130A and130B. When the shutoff of or reduction in power from the power supply isdetected, the magnetic disk device 1 outputs a fault signal to theenable pin EN2 of the regulator 204 and disables (stops) the regulator204. When the regulator 204 is stopped, the operation of the systemcontroller 130B is stopped. When the shutoff of or reduction in powerfrom the power supply 201 is detected, the magnetic disk device 1immediately reduces power consumption by shutting off the power supplyto the system controller 130B and activates PLP power supply. Thus, aPLP process can be performed by only the power consumption of the systemcontroller 130A. In this way, when the power from the power supply 201is shut off or reduced, power can be supplied to the regulator 202before the voltage of the regulator 202 reaches the voltage at which theUVLO operates. This structure prevents the interruption of a PLPprocess. The reliability of the magnetic disk device 1 can be improved.

Now, this specification explains a magnetic disk device according toother embodiments and modification examples. In the other embodimentsand the modification examples, same portions as the above embodiment aredenoted by like reference numbers, detailed description thereof beingomitted.

Second Embodiment

The magnetic disk device 1 of the second embodiment is different fromthe magnetic disk device 1 of the first embodiment in terms of thestructure of a PLP circuit CRT.

FIG. 4 is a block diagram showing an example of the PLP circuit CRTaccording to the second embodiment.

An SVC 203 is electrically connected to a PLP power supply 21, a powersupply 201, the DCDC enable pin EN1 of a regulator 202, a regulator 204,a system controller 130A, a system controller 130B and a reset pin RSTprovided in the system controller 130B as described below. The SVC 203is connected to the reset pin RST of the system controller 130B asdescribed below. When the shutoff of or reduction in power from thepower supply 201 is detected, the SVC 203 outputs a fault signal to thereset pin RST of the system controller 130B.

The system controller 130B comprises an R/W channel 40B, a CPU 60B, aserial interface SRB and the reset pin RST. When a fault signal is inputto the reset pin RST from the SVC 203, the operation of the systemcontroller 130B is stopped (in other words, the system controller 130Bis off or reset).

FIG. 5 is a timing chart showing an example of the PLP process of thePLP circuit CRT shown in FIG. 4. In FIG. 5, the horizontal axisrepresents time. In FIG. 5, the arrow shows the passage of time. FIG. 5shows the reset of the system controller 130B (Slave SoC Reset).

In the examples shown in FIG. 4 and FIG. 5, when the shutoff of orreduction in power from the power supply 201 is detected at timing T1,the SVC 203 outputs a fault signal to the system controller 130A, thesystem controller 130B and the reset pin RST of the system controller130B. When the shutoff of or reduction in power from the power supply201 is detected at timing T1, the SVC 203 outputs a regulator enablesignal to the regulator 204. When a fault signal is received from theSVC 203 in the reset pin RST at timing T1, the operation of the systemcontroller 130B is stopped. When the shutoff of or reduction in powerfrom the power supply 201 is detected at timing T1, the SVC 203 outputsan activation signal to the PLP power supply. When an activation signalis received from the SVC 203, the PLP power supply 21 is activated attiming T2. The PLP power supply 21 supplies power to the regulator 202to maintain the operation of the system controller 130A. It is possibleto prevent the interruption of a PLP process by activating the PLP powersupply 21 at timing T2 before the voltage of the regulator 202 reachesthe master regulator UVLO. In this way, before the UVLO of the regulator202 operates, the PLP power supply 21 is activated, and further, thesystem controller 130B is stopped. Thus, the system controller 130A isconfigured to perform a backup process for storing, in a nonvolatilememory 90, the cache data temporarily stored in a buffer memory 80without interrupting a PLP process.

According to the second embodiment, when the shutoff of or reduction inpower from the power supply is detected, the magnetic disk device 1outputs a fault signal to the reset pin RST of the system controller130B and stops the operation of the system controller 130B. When theshutoff of or reduction in power from the power supply 201 is detected,the magnetic disk device 1 immediately reduces power consumption bystopping the operation of the system controller 130B and activates thePLP power supply. Thus, a PLP process can be performed by only the powerconsumption of the system controller 130A. In this way, when the powerfrom the power supply 201 is shut off or reduced, power can be suppliedto the regulator 202 before the voltage of the regulator 202 reaches thevoltage at which the UVLO operates. This structure prevents theinterruption of a PLP process. The reliability of the magnetic diskdevice 1 can be improved.

Third Embodiment

The magnetic disk device 1 of the third embodiment is different from themagnetic disk device 1 of each of the above embodiments in terms of thestructure of a PLP circuit CRT.

FIG. 6 is a block diagram showing an example of the PLP circuitaccording to the third embodiment.

An SVC 203 is electrically connected to a PLP power supply 21, a powersupply 201, the DCDC enable pin EN1 of a regulator 202, a systemcontroller 130A and a system controller 130B.

When a signal for stopping the operation (in other words, a disablesignal) is received from the system controller 130A via a generalpurpose input/output (GPIO) pin GP (or a DCDC enable pin) as describedlater, the operation of the regulator 204 is stopped (in other words,the regulator 204 is disabled).

The system controller 130A comprises the GPIO pin GP. The systemcontroller 130A is connected to the enable pin EN2 of a regulator 204via the GPIO pin GP. In other words, the GPIO pin GP of the systemcontroller 130A is electrically connected to the enable pin EN2 of theregulator 204. When the shutoff of or reduction in power from the powersupply 201 is detected, for example, when a fault signal is receivedfrom the SVC 203, the system controller 130A receives minimuminformation necessary to prevent an communication error from the systemcontroller 130B via a serial interface SRA. After receiving minimuminformation in the serial interface SRA from the serial interface SRB ofthe system controller 130B, the system controller 130A outputs a disablesignal to the enable pin EN2 of the regulator 204 via the GPIO pin GP.

When the shutoff of or reduction in power from the power supply 201 isdetected, for example, when a fault signal is received from the SVC 203,the system controller 130B outputs minimum necessary information to theserial interface SRA of the system controller 130A via the serialinterface SRB.

FIG. 7 is a timing chart showing an example of the PLP process of thePLP circuit CRT shown in FIG. 6. In FIG. 7, the horizontal axisrepresents time. In FIG. 7, the arrow shows the passage of time. FIG. 7shows a disable signal from the GPIO pin GP of the system controller130A.

In the examples shown in FIG. 6 and FIG. 7, when the shutoff of orreduction in power from the power supply 201 is detected at timing T1,the SVC 203 outputs a fault signal to the system controller 130A and thesystem controller 130B. When a fault signal is received from the SVC 203at timing T1, the system controller 130B outputs minimum necessaryinformation to the serial interface SRA of the system controller 130Avia the serial interface SRB. When a fault signal is received from theSVC 203 at timing T1, and further when minimum necessary information isreceived in the serial interface SRA from the serial interface SRB ofthe system controller 130B, the system controller 130A outputs a disablesignal to the enable pin EN2 of the regulator 204 via the GPIO pin GP.When a disable signal is received in the enable pin EN2 from the GPIOpin GP of the system controller 130A, the operation of the regulator 204is stopped. As power is not supplied from the regulator 204, theoperation of the system controller 130B is stopped. When the shutoff ofor reduction in power from the power supply 201 is detected, the SVC 203outputs an activation signal to the PLP power supply. When an activationsignal is received from the SVC 203, the PLP power supply 21 isactivated at timing T2. The PLP power supply 21 supplies power to theregulator 202 to maintain the operation of the system controller 130A.It is possible to prevent the interruption of a PLP process byactivating the PLP power supply 21 at timing T2 before the voltage ofthe regulator 202 reaches the master regulator UVLO. In this way, beforethe UVLO of the regulator 202 operates, the PLP power supply 21 isactivated, and further, the system controller 130B is stopped. Thus, thesystem controller 130A is configured to perform a backup process forstoring, in a nonvolatile memory 90, the cache data temporarily storedin a buffer memory 80 without interrupting a PLP process.

According to the third embodiment, when the shutoff of or reduction inpower from the power supply 201 is detected, the magnetic disk device 1outputs necessary minimum information from the system controller 130B tothe system controller 130A, outputs a disable signal from the GPIO pinGP of the system controller 130B to the enable pin EN2 of the regulator204 and disables the regulator 204. When the regulator 204 is stopped,the operation of the system controller 130B is stopped. When the shutoffof or reduction in power from the power supply 201 is detected, themagnetic disk device 1 immediately reduces power consumption by stoppingthe operation of the system controller 130 and activates the PLP powersupply. Thus, a PLP process can be performed by only the powerconsumption of the system controller 130A. In this way, when the powerfrom the power supply 201 is shut off or reduced, power can be suppliedto the regulator 202 before the voltage of the regulator 202 reaches thevoltage at which the UVLO operates. This structure prevents theinterruption of a PLP process. The reliability of the magnetic diskdevice 1 can be improved.

Fourth Embodiment

The magnetic disk device 1 of the fourth embodiment is different fromthe magnetic disk device 1 of each of the above embodiments in terms ofthe structure of a PLP circuit CRT.

FIG. 8 is a block diagram showing an example of the PLP circuit CRTaccording to the fourth embodiment.

An SVC 203 is electrically connected to a PLP power supply 21, a powersupply 201, a DCDC enable pin EN1 provided in a regulator 202, aregulator 204, a system controller 130A, a system controller 130B, anenable pin ENA provided in an R/W channel 40A as described later, and anenable pin ENB provided in an R/W channel 40B as described later.

The system controller 130A comprises the R/W channel 40A comprising theenable pin ENA, a CPU 60A and a serial interface SRA. The systemcontroller 130A is electrically connected to a buffer memory 80 and anonvolatile memory 90.

The enable pin ENA of the R/W channel 40A is electrically connected tothe SVC 203. The R/W channel 40A consumes more electricity than, forexample, another unit of the system controller 130A. For example, theR/W channel 40A consumes the most electricity among the units of thesystem controller 130A. When the shutoff of or reduction in power fromthe power supply 201 of the system controller 130A is detected, forexample, when a fault signal is received in the enable pin ENA of theR/W channel 40A from the SVC 203, the operation of the R/W channel 40Ais stopped.

The system controller 130B comprises the R/W channel 40B comprising theenable pin ENB, a CPU 60B and a serial interface SRB. The enable pin ENBof the R/W channel 40B is electrically connected to the SVC 203. The R/Wchannel 40B consumes more electricity than, for example, another unit ofthe system controller 130B. For example, the R/W channel 40B consumesthe most electricity among the units of the system controller 130B. Whenthe shutoff of or reduction in power from the power supply 201 isdetected, for example, when a fault signal is received in the enable pinENB of the R/W channel 40B from the SVC 203, the operation of the R/Wchannel 40B is stopped.

FIG. 9 is a timing chart showing an example of the PLP process of thePLP circuit CRT shown in FIG. 8. In FIG. 9, the horizontal axisrepresents time. In FIG. 9, the arrow shows the passage of time. FIG. 9shows the enable of the R/W channels 40A and 40B.

In the examples shown in FIG. 8 and FIG. 9, when the shutoff of orreduction in power from the power supply 201 is detected at timing T1,the SVC 203 outputs a fault signal to the enable pin ENA of the R/Wchannel 40A, the enable pin ENB of the R/W channel 40B, the systemcontroller 130A and the system controller 130B. When the shutoff of orreduction in power from the power supply 201 is detected at timing T1,the SVC 203 outputs a regulator enable signal to the regulator 204. Whena fault signal is received from the SVC 203 in the enable pin ENA attiming T1, the operation of the R/W channel 40A is stopped. When a faultsignal is received from the SVC 203 in the enable pin ENB at timing T1,the operation of the R/W channel 40B is stopped. When the shutoff of orreduction in power from the power supply 201 is detected at timing T1,the SVC 203 outputs an activation signal to the PLP power supply. Whenan activation signal is received from the SVC 203, the PLP power supply21 is activated at timing T2. The PLP power supply 21 supplies power tothe regulator 202 to maintain the operation of the units of the systemcontroller 130A other than the R/W channel 40A. The PLP power supply 21supplies power to the regulator 204 to maintain the operation of theunits of the controller 130B other than the R/W channel 40B. It ispossible to prevent the interruption of a PLP process by activating thePLP power supply 21 at timing T2 before voltage reaches the masterregulator UVLO. In this way, before the UVLO of the regulator 202operates, the PLP power supply 21 is activated, and the R/W channel 40Aof the system controller 130A is stopped, and further, the R/W channel40B of the system controller 130B is stopped. Thus, the systemcontroller 130A is configured to store, in a nonvolatile memory 90, thecache data temporarily stored in a buffer memory 80 without interruptinga PLP process. The PLP power supply 21 may be configured to supply powerto only the regulator 202 when an activation signal is received.

According to the fourth embodiment, when the shutoff of or reduction inpower from the power supply 201 is detected, the magnetic disk device 1outputs a fault signal to the enable pin ENA of the R/W channel 40A andthe enable pin ENB of the R/W channel 40B and stops the operation of theR/W channels 40A and 40B. When the shutoff of or reduction in power fromthe power supply 201 is detected, the magnetic disk device 1 immediatelyreduces power consumption by stopping the operation of the R/W channel40A of the system controller 130A and the R/W channel 40B of the systemcontroller 130B and activates the PLP power supply. Thus, a PLP processcan be performed by the power consumption of the units of the systemcontroller 130A other than the R/W channel 40A and the units of thesystem controller 130B other than the R/W channel 40B. In this way, whenthe power from the power supply 201 is shut off or reduced, power can besupplied to the regulators 202 and 204 before the voltage of theregulators 202 and 204 reaches the voltage at which the UVLO operates.This structure prevents the interruption of a PLP process. Thereliability of the magnetic disk device 1 can be improved.

Fifth Embodiment

The structure of the magnetic disk device 1 of the fifth embodiment isdifferent from that of the magnetic disk device 1 of each of the aboveembodiments.

FIG. 10 is a block diagram showing the structure of the magnetic diskdevice 1 according to the fifth embodiment.

The magnetic disk device 1 comprises a disk 10, an SPM 12, an arm 13comprising a head 15, a VCM 14, a driver IC 20, a head amplifier IC 30,a volatile memory 70, a buffer memory (buffer) 80, a nonvolatile memory90 and a system controller 130 which is a single-chip integratedcircuit. The magnetic disk device 1 is connected to a host 100. Themagnetic disk device 1 of the fifth embodiment is a normal magnetic diskdevice comprising a single actuator 16.

FIG. 11 is a block diagram showing an example of a PLP circuit CRTaccording to the fifth embodiment.

The PLP circuit CRT is a circuit for performing a PLP process. The PLPcircuit CRT comprises, for example, a PLP power supply 21, the buffermemory 80, the nonvolatile memory 90, the system controller 130, a powersupply 201, a regulator 202 and a servo component (SVC) 203. The PLPcircuit CRT may further comprise the volatile memory 70.

The power supply 201 is electrically connected to the regulator 202 andthe SVC 203. The power supply 201 supplies electricity (power) to theregulator 202 and the SVC 203. For example, the power supply 201supplies a power of 5 V to each of the regulator 202 and the SVC 203.

The regulator 202 is electrically connected to the system controller130. The regulator 202 outputs a particular voltage or current to thesystem controller 130. For example, the regulator 202 outputs 1 V to thesystem controller 130.

The SVC 203 is electrically connected to the PLP power supply 21, thepower supply 201, the DCDC enable pin EN1 of the regulator 202, thesystem controller 130 and the enable pin EN3 of the R/W channel 40 ofthe system controller 130 as described later. For example, the SVC 203outputs 1.8 V and 1.5 V to the system controller 130. When the shutoffof or reduction in power from the power supply 201 is detected, forexample, the SVC 203 outputs a fault signal to the system controller 130and the enable pin EN3 of the R/W channel 40 of the system controller130. When the shutoff of or reduction in power from the power supply 201is detected, the SVC 203 outputs an activation signal to the PLP powersupply.

The PLP power supply 21 is electrically connected to the regulator 202and the SVC 203. When an activation signal is received from the SVC 203,the PLP power supply 21 is activated and supplies power to at least theregulator 202.

The buffer memory 80 is connected to the system controller 130. Thenonvolatile memory 90 is connected to the system controller 130.

The system controller 130 comprises the R/W channel 40 and a CPU 60. Thesystem controller 130 is electrically connected to the buffer memory 80and the nonvolatile memory 90. When the shutoff of or reduction in powerfrom the power supply 201 is detected, for example, when a fault signalis received from the SVC 203, the system controller 130 performs abackup process for saving the cache data stored in the buffer memory tothe nonvolatile memory 90.

The R/W channel 40 performs a signal process of read data transferredfrom the disk 10 to the host 100 and write data transferred from thehost 100 in response to an instruction from the CPU 60 as describedlater. The R/W channel 40 comprises a circuit or function for evaluatingthe signal quality of read data. The R/W channel 40 comprises an enablepin EN3. When a fault signal is input to the enable pin EN3 from the SVC203, the operation of the R/W channel 40 is stopped (in other words, theR/W channel 40 is off).

The CPU 60 is a main controller which controls the units of the magneticdisk device 1 in response to an instruction from the host 100, etc. TheCPU 60 performs servo control by controlling the actuator via the driverIC 20 to determine the position of the head 15. The CPU 60 controls datawrite to the disk 10 and selects the storage destination of write data.The CPU 60 controls data read from the disk 10 and controls the processof read data. The CPU 60 is connected to the units of the magnetic diskdevice 1. The CPU 60 is electrically connected to, for example, thedriver IC 20 and the R/W channel 40.

In the example shown in FIG. 11, when the shutoff of or reduction inpower from the power supply 201 is detected, the SVC 203 outputs a faultsignal to the system controller 130 and the enable pin EN3 of the R/Wchannel 40. When a fault signal is received in the enable pin EN3 fromthe SVC 203, the operation of the R/W channel 40 is stopped. When theshutoff of or reduction in power from the power supply 201 is detected,the SVC 203 outputs an activation signal to the PLP power supply. Whenan activation signal is received from the SVC 203, the PLP power supply21 is activated. The PLP power supply 21 supplies power to the regulator202 to maintain the operation of the system controller 130. As the PLPpower supply 21 is activated after the operation of the R/W channel 40is stopped, the system controller 130 is configured to reduce thenecessary power consumption and perform a backup process for storing, inthe nonvolatile memory 90, the cache data temporarily stored in thebuffer memory 80.

According to the fifth embodiment, when the shutoff of or reduction inpower from the power supply 201 is detected, the magnetic disk device 1outputs a fault signal to the system controller 130 and the enable pinEN3 of the R/W channel 40 and stops the operation of the R/W channel 40.When the shutoff of or reduction in power from the power supply 201 isdetected, the magnetic disk device 1 immediately reduces powerconsumption by stopping the operation of the R/W channel 40 of thesystem controller 130 and activates the PLP power supply. Thus, a PLPprocess can be performed by the power consumption of the units of thesystem controller 130 other than the R/W channel 40. In this way, themagnetic disk device 1 is configured to perform a PLP process with lessenergy.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. A magnetic disk device comprising: a disk; firstand second heads which write data to the disk and read data from thedisk; a first actuator comprising the first head; a second actuatorcomprising the second head; first and second controllers which controlthe first head, the second head, the first actuator and the secondactuator; an auxiliary power supply which supplies power when power froma power supply is shut off; and a power supply detection unit whichmakes power supplied from the auxiliary power supply to the firstcontroller higher than the power supplied from the auxiliary powersupply to the second controller when shutoff of power from the powersupply is detected; wherein the power supplied from the auxiliary powersupply to one of the first and second controllers is reduced immediatelyafter the power from the power supply is shut off.
 2. The magnetic diskdevice of claim 1, further comprising: a first power supply unit whichis electrically connected to the power supply, the auxiliary powersupply and the first controller, and supplies power to the firstcontroller; and a second power supply unit which is electricallyconnected to the power supply, the auxiliary power supply and the secondcontroller, and supplies power to the second controller, wherein thepower supply detection unit stops the second power supply unit whenshutoff of power from the power supply is detected.
 3. The magnetic diskdevice of claim 2, wherein the second power supply unit comprises anenable pin, wherein the power supply detection unit is electricallyconnected to the enable pin, and outputs a fault signal to the enablepin when shutoff of power from the power supply is detected.
 4. Themagnetic disk device of claim 3, wherein the auxiliary power supplysupplies power to the first power supply unit before a first voltage atwhich a low-voltage abnormal operation prevention function operates isreached.
 5. The magnetic disk device of claim 1, further comprising: afirst power supply unit which is electrically connected to the powersupply, the auxiliary power supply and the first controller, andsupplies power to the first controller; and a second power supply unitwhich is electrically connected to the power supply, the auxiliary powersupply and the second controller, and supplies power to the secondcontroller, wherein the first controller stops the second power supplyunit when power from the power supply is shut off.
 6. The magnetic diskdevice of claim 5, wherein the second power supply unit comprises anenable pin, the power supply detection unit outputs a fault signal tothe first controller when shutoff of power from the power supply isdetected, and the first controller comprises a GPIO pin, is electricallyconnected to the enable pin via the GPIO pin, and outputs a signal tothe enable pin via the GPIO pin when the fault signal is received fromthe power supply detection unit.
 7. The magnetic disk device of claim 1,wherein the power supply detection unit stops the second controller whenshutoff of power from the power supply is detected.
 8. The magnetic diskdevice of claim 7, wherein the second controller comprises a reset pin,and the power supply detection unit is electrically connected to thereset pin, and outputs a fault signal to the reset pin when shutoff ofpower from the power supply is detected.
 9. The magnetic disk device ofclaim 1, wherein the first controller comprises a first read/writechannel, the second controller comprises a second read/write channel,and the power supply detection unit stops the first read/write channeland the second read/write channel when shutoff of power from the powersupply is detected.
 10. The magnetic disk device of claim 9, wherein thefirst read/write channel comprises a first enable pin; the secondread/write channel comprises a second enable pin; and the power supplydetection unit outputs a fault signal to the first enable pin and thesecond enable pin when shutoff of power from the power supply isdetected.
 11. The magnetic disk device of claim 2, further comprising: avolatile memory electrically connected to the first controller; and anonvolatile memory electrically connected to the first controller.